/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.multipart.support;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.Serializable;
import java.io.UnsupportedEncodingException;
import java.nio.file.Files;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Enumeration;
import java.util.LinkedHashMap;
import java.util.LinkedHashSet;
import java.util.Map;
import java.util.Set;

import javax.mail.internet.MimeUtility;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.Part;

import org.springframework.http.ContentDisposition;
import org.springframework.http.HttpHeaders;
import org.springframework.lang.Nullable;
import org.springframework.util.FileCopyUtils;
import org.springframework.util.LinkedMultiValueMap;
import org.springframework.util.MultiValueMap;
import org.springframework.web.multipart.MaxUploadSizeExceededException;
import org.springframework.web.multipart.MultipartException;
import org.springframework.web.multipart.MultipartFile;

/**
 * Spring MultipartHttpServletRequest adapter, wrapping a Servlet 3.0 HttpServletRequest
 * and its Part objects. Parameters get exposed through the native request's getParameter
 * methods - without any custom processing on our side.
 *
 * @author Juergen Hoeller
 * @author Rossen Stoyanchev
 * @since 3.1
 */
public class StandardMultipartHttpServletRequest extends AbstractMultipartHttpServletRequest {

    @Nullable
    private Set<String> multipartParameterNames;


    /**
     * Create a new StandardMultipartHttpServletRequest wrapper for the given request,
     * immediately parsing the multipart content.
     *
     * @param request the servlet request to wrap
     * @throws MultipartException if parsing failed
     */
    public StandardMultipartHttpServletRequest(HttpServletRequest request) throws MultipartException {
        this(request, false);
    }

    /**
     * Create a new StandardMultipartHttpServletRequest wrapper for the given request.
     *
     * @param request the servlet request to wrap
     * @param lazyParsing whether multipart parsing should be triggered lazily on
     * first access of multipart files or parameters
     * @throws MultipartException if an immediate parsing attempt failed
     */
    public StandardMultipartHttpServletRequest(HttpServletRequest request,
            boolean lazyParsing) throws MultipartException {

        super(request);
        if (!lazyParsing) {
            parseRequest(request);
        }
    }


    private void parseRequest(HttpServletRequest request) {
        try {
            Collection<Part> parts = request.getParts();
            this.multipartParameterNames = new LinkedHashSet<>(parts.size());
            MultiValueMap<String, MultipartFile> files = new LinkedMultiValueMap<>(parts.size());
            for (Part part : parts) {
                String headerValue = part.getHeader(HttpHeaders.CONTENT_DISPOSITION);
                ContentDisposition disposition = ContentDisposition.parse(headerValue);
                String filename = disposition.getFilename();
                if (filename != null) {
                    if (filename.startsWith("=?") && filename.endsWith("?=")) {
                        filename = MimeDelegate.decode(filename);
                    }
                    files.add(part.getName(), new StandardMultipartFile(part, filename));
                } else {
                    this.multipartParameterNames.add(part.getName());
                }
            }
            setMultipartFiles(files);
        } catch (Throwable ex) {
            handleParseFailure(ex);
        }
    }

    protected void handleParseFailure(Throwable ex) {
        String msg = ex.getMessage();
        if (msg != null && msg.contains("size") && msg.contains("exceed")) {
            throw new MaxUploadSizeExceededException(-1, ex);
        }
        throw new MultipartException("Failed to parse multipart servlet request", ex);
    }

    @Override
    protected void initializeMultipart() {
        parseRequest(getRequest());
    }

    @Override
    public Enumeration<String> getParameterNames() {
        if (this.multipartParameterNames == null) {
            initializeMultipart();
        }
        if (this.multipartParameterNames.isEmpty()) {
            return super.getParameterNames();
        }

        // Servlet 3.0 getParameterNames() not guaranteed to include multipart form items
        // (e.g. on WebLogic 12) -> need to merge them here to be on the safe side
        Set<String> paramNames = new LinkedHashSet<>();
        Enumeration<String> paramEnum = super.getParameterNames();
        while (paramEnum.hasMoreElements()) {
            paramNames.add(paramEnum.nextElement());
        }
        paramNames.addAll(this.multipartParameterNames);
        return Collections.enumeration(paramNames);
    }

    @Override
    public Map<String, String[]> getParameterMap() {
        if (this.multipartParameterNames == null) {
            initializeMultipart();
        }
        if (this.multipartParameterNames.isEmpty()) {
            return super.getParameterMap();
        }

        // Servlet 3.0 getParameterMap() not guaranteed to include multipart form items
        // (e.g. on WebLogic 12) -> need to merge them here to be on the safe side
        Map<String, String[]> paramMap = new LinkedHashMap<>();
        paramMap.putAll(super.getParameterMap());
        for (String paramName : this.multipartParameterNames) {
            if (!paramMap.containsKey(paramName)) {
                paramMap.put(paramName, getParameterValues(paramName));
            }
        }
        return paramMap;
    }

    @Override
    public String getMultipartContentType(String paramOrFileName) {
        try {
            Part part = getPart(paramOrFileName);
            return (part != null ? part.getContentType() : null);
        } catch (Throwable ex) {
            throw new MultipartException("Could not access multipart servlet request", ex);
        }
    }

    @Override
    public HttpHeaders getMultipartHeaders(String paramOrFileName) {
        try {
            Part part = getPart(paramOrFileName);
            if (part != null) {
                HttpHeaders headers = new HttpHeaders();
                for (String headerName : part.getHeaderNames()) {
                    headers.put(headerName, new ArrayList<>(part.getHeaders(headerName)));
                }
                return headers;
            } else {
                return null;
            }
        } catch (Throwable ex) {
            throw new MultipartException("Could not access multipart servlet request", ex);
        }
    }


    /**
     * Spring MultipartFile adapter, wrapping a Servlet 3.0 Part object.
     */
    @SuppressWarnings("serial")
    private static class StandardMultipartFile implements MultipartFile, Serializable {

        private final Part part;

        private final String filename;

        public StandardMultipartFile(Part part, String filename) {
            this.part = part;
            this.filename = filename;
        }

        @Override
        public String getName() {
            return this.part.getName();
        }

        @Override
        public String getOriginalFilename() {
            return this.filename;
        }

        @Override
        public String getContentType() {
            return this.part.getContentType();
        }

        @Override
        public boolean isEmpty() {
            return (this.part.getSize() == 0);
        }

        @Override
        public long getSize() {
            return this.part.getSize();
        }

        @Override
        public byte[] getBytes() throws IOException {
            return FileCopyUtils.copyToByteArray(this.part.getInputStream());
        }

        @Override
        public InputStream getInputStream() throws IOException {
            return this.part.getInputStream();
        }

        @Override
        public void transferTo(File dest) throws IOException, IllegalStateException {
            this.part.write(dest.getPath());
            if (dest.isAbsolute() && !dest.exists()) {
                // Servlet 3.0 Part.write is not guaranteed to support absolute file paths:
                // may translate the given path to a relative location within a temp dir
                // (e.g. on Jetty whereas Tomcat and Undertow detect absolute paths).
                // At least we offloaded the file from memory storage; it'll get deleted
                // from the temp dir eventually in any case. And for our user's purposes,
                // we can manually copy it to the requested location as a fallback.
                FileCopyUtils.copy(this.part.getInputStream(), Files.newOutputStream(dest.toPath()));
            }
        }
    }


    /**
     * Inner class to avoid a hard dependency on the JavaMail API.
     */
    private static class MimeDelegate {

        public static String decode(String value) {
            try {
                return MimeUtility.decodeText(value);
            } catch (UnsupportedEncodingException ex) {
                throw new IllegalStateException(ex);
            }
        }
    }

}
